Weather conditions cause considerable damage to buildings and other structures. A common source of damage is windloads created during storms or other weather events. As a result, efforts have been made to strengthen structures to prevent damage. Since garage doors, unlike the walls of a building, are unsupported over large spans, these doors and other similar movable barriers have been identified as a possible component of a structure that, if strengthened, could reduce damage to the structure.
To address this problem, reinforced door designs have been made. In general, these designs seek to stiffen the door by providing a thicker door or adding beams and struts positioned on the door, usually horizontally, such that, the stresses created by wind velocity pressures are transmitted to the beams and struts. Typically, these beams and struts are made of solid wood members or channel-like steel members. The weight of the beams and struts along with the components necessary to mount them often double or triple the weight of a non-windloaded door. As will be appreciated, the additional beams and struts also add considerable cost. As a result of the door's increased weight, additional strength must be added to the other components of the door system, such as the counterbalance springs, the guide tracks, and the rollers. Moreover, the door support structure must be capable of supporting the additional weight. Finally, the additional weight makes the entire door system more cumbersome and difficult to install. While a single installer can ordinarily install a non-windload door, a door reinforced with beams and struts typically requires at least two installers because of the added weight.
Aside from the increased weight, the beams and struts protrude inward from the door taking up space inside of the garage and requiring additional clearance for opening and closing of the door. This additional clearance reduces the usable length and head room of the structure making it difficult, for example, to park larger vehicles, such as sport utility vehicles within the structure.
In terms of aesthetics, the beams and struts detract from the appearance of the door and the structure.
Another door design used to deal with windloads incorporates “windlocks.” Windlocks are locking devices located on a portion of a door section or panel that can either ride in or lock the door to the track system or lock the door to a supporting jamb when the door is closed. In this way, the windlocks transfer stresses generated by wind velocity pressure to the jamb or structure. If reinforcing beams or struts are also added to the door, the stresses will be more generally distributed about the door and the supporting jamb
Windlocks are commonly used in rolling doors because a rolling door storage means prevents the adding of sufficient strength by using beams or struts. A rolling door uses a section or slat profile that has a male edge and a female edge that form a continuous hinge along the width of the door. This hinge has a thickness of at least two facers and provides an amount of stiffness to the sections or slats. Windlocks can be added at the end of these sections or slats to improve the door's resistance to wind velocity pressures by transmitting the stresses on the continuous hinge area to the ends of the sections and through the windlocks to the supporting guide system and finally to the jamb or building structure. These windlocks are larger in cross section than the slats and, when the door deflects from high wind velocity pressures, the windlocks are designed to engage the track in which the slats are received. When storing a rolling door equipped with windlocks, additional room is needed because of the depth of the windlock relative to that of the slats. As a result, the stored door has an increased diameter and takes up additional interior space. In these designs, clearance between the windlock and the track must be provided to prevent the windlocks from jamming door travel and care must be taken when operating the door in wind because the windlocks will jam as the door deflects. Normally, rolling door sections are 2 to 6 inches high with a large number of hinges and windlocks being necessary for a 7 to 8 foot garage door. As a result, accurate alignment of the windlocks must be made to prevent them from unintentionally striking the track system or affecting operation of the door. Improper alignment can also cause the rolling door to jam and prevent the door from operating properly. Any damage to the slats or sections caused by misalignment can also prevent the door from closing properly.
Windload systems using windlocks or horizontal reinforcement members that transfer forces to the jambs or building structure are limited in the amount of wind velocity pressure they can withstand. While the horizontal support decreases the vertical span, the strength of the door is still limited by the horizontal span. More recent prior art designs use vertical reinforcing posts to improve wind resistence by dividing the horizontal span and transferring a portion of the load to floor and the header above the door. In contrast to the horizontal support designs, the vertical support designs keep the door rigid rather than flexible under forces from the wind and transmit stresses that are parallel to the direction of the wind. Although these reinforcing post designs are always active, they add noise during the movement cycles and they suffer the same weight and clearance disadvantages of using beams and struts as mentioned above. Moreover, these permanently attached reinforcing posts add unsupported weight to the door when the door is in the open or horizontal position making it necessary to use horizontal supports on the door to prevent it from sagging.
Overall, with the exception of rolling doors, the windload design efforts have been directed at making the door sections in the door as stiff or rigid as possible with either horizontal or vertical supports. Generally, the stress transmitted to the jambs or building structure run parallel to the direction of the wind and have been known to cause a door to deflect. If the door deflects more than 6 to 8 inches under wind velocity pressure, the door likely will buckle and no longer be useable. As a result, existing design work has focused on this deflection limit as a basis to establish adequate door strength or stiffness.
In view of the shortcomings noted above in regard to use of additional beams and struts, and wind lock configurations, it is evident that there is a need in the art for a door support system which is minimal in weight, allows the door to function in a normal or close-to-normal operating manner. It will further be appreciated that there is a need for restraining the sections of a sectional overhead door that will keep the door sections in tension when exposed to wind velocity pressures when the door is closed as a means of distributing forces to prevent premature buckling of the sections. It will also be appreciated that the structure and associated method for restraining the sections needs to be quick and easily installed and can be active at all times when the door is closed.